The present invention relates generally to the art of forming bells on plastic pipes, and more particularly, is directed to an apparatus suitable to form an internal groove simultaneously with the belling of the pipe.
It is the usual practice to extrude plastic pipes in elongate configuration of desired diameter and then to cut the extruded product into individual lengths of convenient size suitable for handling, shipping and installing, for example twenty foot lengths. As each length of pipe is cut, it is presently the practice to enlarge or "bell" one end sufficiently to join adjacent pipe sections by receiving an unenlarged end of another similar length of pipe therein. The inside diameter of the bell is formed sufficiently large to receive easily one end of the next adjacent section of pipe with sufficient clearance to allow the application of packing, sealing materials, gaskets or other materials designed to prevent leakage at the pipe joints when the pipe lengths are joined to form a pipe line. In many applications, the seal between adjacent lengths of pipe is provided by expanding an internal groove in the bell of suitable configuration and design to seat therein an annular, resilient gasket to permit a leak proof pipe joint to be easily and rapidly made in the field.
It is usual to employ a single mandrel construction both to form the shaped bell, and at the same time, to simultaneously also form the expanded groove for receipt therein of the annular gasket. U.S. Pat. No. 4,238,180 entitled "Mandrel with Identical Expanding Segments", which is commonly assigned to the assignee of the present application, is exemplary of prior art belling machines including the capability of simultaneously forming a pipe bell including an integral gasket receiving groove.